11 June, 1917.] Apple Culture in Victoria. 



343 



Functions of the Leaves. 



The leaves are so arranged in the tree's structure in relation to the 

 sap-wood and to the c-anibiuni that they are enabled to receive the crude 

 sap through the niediuni of the former channel, and to distribute it when 

 elaborated by means of the latter to the various parts of the tree where 

 new structures are being built up. 



Plate 100.— Same leaf as in Plate 99, but showing under surface. 



When the liquid food ascends to the foot stalks of the leaves it is 

 passed on the midribs and by means of the lateral ribs to the veins and 

 veinlets, which in turn supply the cell tissue in the upper surface of the 

 leaves. Here the crude sap meets with the carbon which the leaves 

 obtain by breathing in carbonic acid from the air through the stomata 

 in the leaf epidermis during the day time while they are open. 



